Two-step synthesis, structure and adsorption property of a dynamic zinc phosphonocarboxylate framework

Two zinc phosphonocarboxylate frameworks, Zn(1.5)(pbc)(2,2'-bpy) (1) (2,2'-bpy = 2,2'-bipyridine) and Zn(pbc)(NH(2)(CH(3))(2))(0.5)center dot 0.5H(3)O (2), were synthesized in a mixed-solvothermal condition. Their structures have been determined by single-crystal X-ray diffraction analysis, IR spectra and thermogravimetric analysis. Compound 1 is a three-dimensional zinc phosphonocarboxylate with auxiliary ligand of 2,2'-bpy. 2 was obtained by reheating the filtrate of 1 and shows a nanoporous open-framework with zeolitic GIS topology. At room temperature, 2 can absorb organic amine and solvents in its channels, causing a breathing effect and shrinkage of the pores, resulting in single-crystal-tosingle- crystal transformation to structure 2a, Zn(pbc)(NH(2)(CH(3))(2))center dot 0.5DMF center dot 2H(2)O. The porosity of 2 was demonstrated by the methanol and water adsorption experiments, indicating selective guest uptake.